In recent years, a light emitting diode (LED) lamp has been undergoing a rapid growth and gradually stepping into the general illumination market. Compared with a conventional incandescent tungsten filament bulb and a fluorescent lamp, an LED lamp makes use of the superiority in small size, energy-saving, environment-friendly and long lifespan to achieve an appellation of green light source.
Referring to FIG. 1, a structural view of a conventional optical lens applied in an LED lamp. As shown in FIG. 1, an optical lens 10 includes a mounting pedestal 11, a dome structure 13 disposed on the mounting pedestal 11, and a protrusion structure 15 outwardly protruding from the dome structure 13 along a direction away from the mounting pedestal 11. The dome structure 13 has an external surface 131, the protrusion structure 15 has a first optical surface 151, a first optical side 153, a second optical surface 155 and a second optical side 157. The first optical surface 151, the first optical side 153, the second optical surface 155 and the second optical side 157 are connected successively. The first optical side 153 and the second optical side 157 are perpendicular to the external surface 131 of the dome structure 13.
However, referring to FIG. 2, it is alight pattern simulation diagram of the optical lens 10 shown in FIG. 1. As seen from FIG. 2, it can be found that ray L1 in rays from the optical lens 10 is radiating along a direction close to the horizontal line, when the optical lens 10 is applied as a streetlight, the ray L1 will not hit the road, which can cause loss in optical efficiency.